Cable joint for optical fibers with splicing cassettes and overlength loops

ABSTRACT

The invention relates to a cable closure for optical-fiber cables, preferably optical-fiber minicables or optical-fiber microcables, with cable lead-in units, which are arranged perpendicularly with respect to the axis of the closure body, and it is possible for the closure to be fitted vertically into a core hole made into the earth or into road surfacings. On account of laid-in excess lengths of optical waveguide, splice organizers in the interior of the closure body can be taken out upwards for service work. Preferably, the excess lengths of optical waveguide are carried in a protective tube, which is deposited in a plurality of loops in the interior of the closure.

BACKGROUND OF THE INVENTION

The invention relates to an optical-fibre transmission system comprisinga cable closure for optical waveguides with splice organizers andexcess-length depositories for excess lengths of optical waveguide andcomprises at least one optical-fibre cable, cable lead-in units in theform of cable lead-in spigots being arranged into the cable closureperpendicularly with respect to the axis of the closure body of thecable closure, the excess lengths of optical waveguide and the spliceorganizers being arranged within the closure body removably in the axialdirection of the closure body, and at least one end face of the closurebody being closed off in a sealing manner by an externally accessiblecover.

DE 39 04 232-A1 discloses cross-connecting and branching accessories forcommunication cables and distribution networks, and the accessories havea branching junction box and at least one branch cable closure housedtherein. The accessory has a hood closure with customary cable lead-inseals, and the cables led into the branching junction box are laid withexcess lengths so that the hood closure can be taken out for servicework. The cables are fed to the hood closure via separately laid cableducts, and corresponding excess lengths of the cables are deposited inthe cable junction box or manhole before they are led into the hoodclosures. For service work, the hood closures are lifted or swung out oftheir manhole position, so that the hood closure in then accessible andcan be opened. However, such cable installations are designed for anormal laying method of freely layable cables.

U.S. Pat. No. 4,709,980 discloses a cable closure in which the cablelead-ins of the optical waveguides are arranged perpendicularly withrespect to the axis of the cable closure. Contained therein are spliceorganizers, which can be removed upwards after opening a cover.

German Patent Specification 41 40 701 C1 discloses a cable closure as anunderfloor container in which the cable lead-ins take placeperpendicularly with respect to the cable closure axis, and the lead-insare performed via lead-through flanges, so that the cables also have tobe provided with corresponding units. Organizers which can be removedupwards are likewise included here.

EP-A-0 532 980 discloses a hood closure with lead-in spigots which,running in obliquely from below, are fitted into a base plate of thehood closure. Such a cable closure in designed for use in cable shaftsand, if appropriate, for fastening to masts.

JP-04289451 describes a protective housing for a cable closure arrangedin the ground. This protective housing comprises annular componentswhich are arranged on a base. The closure is mounted therein on a frameand surrounded with filling material.

JP-61148782 describes a cable closure in which optical-fibre cables areled in axially. The cable closure comprises a lead housing and isdesigned such that organizer arrangements for excess lengths of opticalwaveguide can be arranged to lie therein. This cable closure isparticularly suitable for use in cases where there are great temperaturechanges. The seals are established by welding.

SUMMARY OF THE INVENTION

The object of the invention is, however, to provide a cable closure foroptical waveguides which is suitable for easy-to-lay minicables ormicrocables, and these minicables or microcables comprise pipes in whichoptical waveguides or optical waveguide bundles are loosely led in. Theobject set is achieved according to a first way with a cable closure ofthe type explained at the beginning by the cable lead-in units beingdesigned as lead-in spigots in the form of pipes tightly fitted on, bythe optical-fibre cables in the form of optical waveguide minicables oroptical waveguide microcables, respectively comprising a pipe andoptical waveguides, optical waveguide strips or optical waveguidebundles loosely introduced therein, being arranged in the cable lead-inunits designed in terms of pipe connecting technology for receiving andsealing off the pipes of the optical-fibre cables, and the sealingconnection of the pipe connecting technology being a welded, soldered oradhesively bonded connection between the pipe of the optical-fibre cableand the cable lead-in unit.

The object set is, however, also achieved according to a second andthird way of forming the sealing connections by a press connection witha union nut, a plastic crimped connector or an elastic annular seal.

The new type of design of optical-fibre cables as minicables ormicrocables allows considerable advantages to be achieved in terms oflaying technology. For instance, first and foremost there is a drasticreduction in costs, since the thin pipes of the optical-fibre cables canbe laid in slits which are easy to make in the surface of the ground, sothat a distinct reduction in the overall line costs for a newinstallation is possible. In addition, an increase in the operationalreliability is possible by redundant routing, which is particularlysuitable if a ring form of network structure is implemented.

For example, by using optical switches to connect up to existingnetworks, these easy-to-lay microcables allow flexible and intelligentnetworks to be built up in a simple way. Simple pigtail rings withoptical switching can be used in this case, so that optical fibres canbe used right up to the final subscriber. The great advantage is alsothat these simple microcables can be introduced at a later time intoroads, pavements, kerb-stones, in the plinth region of walls of housesand special routes. In such cases it is possible to put into practice atechnical concept adapted according to the wishes of the operator,allowing account to be taken of existing infrastructure with respect torights of way, pipes for waste water, gas and district heating. Thelaying of the microcables is particularly easy to manage in thisrespect, since the pipe diameter of the microcables is only between 3.5and 5.5 mm, so that a cutting width of 7 to 10 mm is adequate for thelaying channel to be made. Such a laying channel can be accomplishedwith commercially available cutting machines, a, cutting depth of about70 mm being quite sufficient. The pipe of such a minicable or microcablemay consist of plastic, steel, chromium-nickel-molybdenum alloys,copper, copper alloys (brass, bronze, etc.), aluminium or similarmaterials. The cable closures according to the invention are preferablycylindrically designed and are fitted perpendicularly into a core holecut out for this purpose and having a diameter corresponding to thecable closure, the core hole preferably being about 10 to 30 mm greaterthan the diameter of the cable closures. The closure height of the cableclosure is about 200 mm, it preferably being designed in a pot shape andpointing with its end-face opening towards the surface, which openingcan then be closed off in a pressure-watertight manner with the aid of acover and a seal. The closure body itself is inserted for example by upto ⅔ of its height into a concrete bed and thereby receives adequateanchorage. The upper part of the core hole is then plugged with leanconcrete, hot bitumen, two-component casting compound or expandableplastics materials. The closure cover may also be designed to withstandloading, but a separate covering with an additional manhole cover inalso possible. It is consequently a pressure-water-tight cable closurewhich can be opened and reclosed at any time and has special cablelead-in units for minicables or microcables. The cross-connection excesslength of the optical fibres or excess length of optical waveguides forsubsequent splicing and all optical-fibre splices are accommodated inthe closure body itself, these splices being mounted on a correspondingsplice organizer. This splice organizer can be removed upwards in theaxial direction of the cable closure, so that the closure itself canremain in its position. The optical waveguides are protected by aflexible tube, so that there is no risk of buckling during service work.For example, up to four tubular microcables may be led into the cableclosure, the cable lead-in units for this purpose preferably beingarranged on one side of the closure housing such that a tangentialleading in of the optical waveguides along the inner wall of the closureis possible. The radius of the cable closure in this case corresponds atleast to the minimum permissible bending radius of the opticalwaveguides, so that no additional protective devices have to beprovided. The cable lead-in units comprise, for example, soft-metaltubes fitted in a sealtight manner into the wall of the closure, theends of which tubes are plastically deformed by crimping on the led-inmicrocable ends such that a pressure-watertight seal is produced. In thecase of such a pressure-watertight connection, the microcable with itspipe is additionally fixed adequately against tensile, compressive andtorsional stresses. To be able to allow for tolerances in the laying ofthe microcable, the microcable is in each case provided with anelongation loop before it is led into the cable closure, so that as aresult length compensation can take place. Such an elongation loop isprovided before the cable closures or before bends in the microcable.Such an elongation loop may be additionally provided with a metallicprotective tube, which allows only buckle-free bends, so that it ispossible to dispense with further bending tools during installation.These length compensation loops for microcables also compensate forpossibly occurring elongations or shrinkages of the cable, as well assettling in the road or in the earth. They likewise comprise readilybendable metal tubes, for example of copper, and can be made pliable byprior heat treatment in the bending region. It is also possible to makethe tubes used for the length compensation loops, flexible bycorresponding coiling. Metal tubes also accomplish stability againsttransverse compressive stress and ensure that minimum bending radii ofthe optical waveguides are maintained. In addition, the lengthcompensation loops may already be prefabricated at the factory andconsequently no longer need to be produced on site. During laying,

the microcables may also be brought up to and fixed to the closure aboveground, the length compensation loop then receiving the excess length ofcable when the cable closure is lowered. Depending on the configurationand requirements, such an in-line or branch cable closure may beproduced on site with T-shaped or else cross-shaped branches beingpossible.

To realize the invention, slender, elongate closures may be used, inparticular if it is a case of lengthening and repairing a microcable. Inthe case of such in-line cable closures, adaptations of microcables ofdifferent diameters can also be performed. For example, such a cableclosure may on one lead-in side have a microcable of a first diameterled into it in a sealing manner and on the second side of the cableclosure be lengthened by a microcable of a second diameter, differentfrom the first diameter. The adaptation to the different diameters maytake place with the aid of lead-in elements of different diameters orwith the aid of adapted adapter pieces or adapter pipes.

Particularly advantageous are, however, in this case, round, cylindricalclosure bodies, the axis of which however runs perpendicularly withrespect to the axis of the laying direction. In this way, themicrocables may be led into the closure through tangentially arrangedcable lead-in units. As a result, it is also possible to bring togetherin a single closure microcables from different laying depths. Within theclosure, it is also possible for example to realize the splicingtechnique for uncut microcables, the excess lengths of fibre thenexpediently being deposited in a clearly arranged way in a plurality ofloops one above the other within the closure.

In the case of such cable closures according to the invention, it isalso of advantage that the cable lead-in units, and consequently theseals of the cables to be led in, are independent of the end-face

cylinder seal of the cable closure. In addition, each tubular microcableis individually sealed off and the cables lead-in units are preferablyarranged in the middle or lower part of the cable closure, in order thatno crossings of excess lengths of fibre or fibre run-ins occur. Thestorage space for the excess lengths of optical waveguide is preferablyarranged directly underneath the cover, it being possible additionallyto use separating plates, to be able, for example, to separate incomingoptical waveguides from outgoing optical waveguides. In this way, thesplicing space can also be divided off. When taking out the splices forservice work, in each case the excess lengths of optical waveguide mustalways be taken out first, to allow splicing work to be performed. Thesplices may subsequently be accommodated vertically or horizontally in asplicing space, expediently being arranged on a splice organizer, anwhich excess lengths of optical waveguide may also be arranged in aclear manner.

The cable closure according to the invention may, also comprise aplurality of rings, which may be placed one above the other, dependingon size requirements one against the other. The individual rings arethen sealed off with respect to one another, for example by sealingmeasures which are normal and known per se. In the case of such adividable cable closure, uncut cables may also be inserted if leading intakes place in this plane of intersection. This provides the possibilityfor application of the splicing technique.

This new technique thus gives rise to various special features. Forinstance, the cable closures according to the invention can beintroduced into the road surfacing in a simple way in standard coreholes, the composite structure of the carriageway surfacing not beingdestroyed by this core-hole drilling. The laying of the minicables ormicrocables and the associated closures may be performed in a simple wayin any areas of the earth or of the road, preferably along a jointbetween the carriageways, introduced in channels or core holes. In thecase of such a laying technique, the basic structure of the carriage waysurfacing is not disturbed. Earth is not removed. Compaction of theearth is not required. Sinking of the repair site due to settlement innot to be expected. Cracking up or crack propagation is not to beexpected. Laying in a laying channel made with customary cuttingmachines is a simple operation and closing is performed, for example, bypouring in hot bitumen or other fillers. The compact structural designand the relatively small diameter of the cable closure provide adequateload-bearing strength, the sealing of the round closure fastening notpresenting any difficulties, since the cover seal is separate from thecable seals. So-called fibre handling and the fibre run-in may takeplace on a plurality of mutually separate levels, so that betterutilization of the volume of the closure can be achieved. The radius ofthe inner wall of the closure is designed such that it supports theincoming optical waveguides, buckling not being possible.

Elongate cable closures for the connections technique with themicrocables used are suitable in particular for through-connections orwhen lengthening microcables with different materials or different pipediameters. It is possible, for example, even in domestic cable laying toconnect to elongate closures so-called “blown fibre conductors”.

Round, cylindrical closures are suitable in particular for changes indirection in the running of the cables, for cross-connecting, splicing,measuring, branching, dividing, overcoming differences in height in thecase of laid microcables and for receiving optical switches and theelectronics for the transmission technology.

Other advantages and features of the invention will be readily apparentfrom the following description of the preferred embodiments, thedrawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of an elongate closure formicrocables of the same diameters,

FIG. 2 is a longitudinal cross-sectional view of an elongate closure formicrocables of different diameters,

FIG. 3 is a longitudinal cross-sectional view of an elongate closurewith a microcable fitted on one side,

FIG. 4 is a plan view of a cylindrical closure,

FIG. 5 is a plan view of a cylindrical closure with a storage space forexcess lengths of optical waveguide and depositing and fastening of thesplices,

FIG. 6 is a longitudinal cross-sectional view of a cylindrical closure,

FIG. 7 is a longitudinal cross-sectional view of a cylindrical closurewith pulled-out excess lengths of optical waveguides,

FIG. 8 is a cross-sectional view of a round closure with cable lead-inunits at different levels,

FIG. 9 is a cross-sectional view of a round closure, which is cut in theleading-in direction and is suitable for the splicing technique,

FIG. 10 is a cross-sectional view of an extendable round closure,

FIG. 11 shows a cylindrical closure with compensation loops andtangential cable lead-in units,

FIG. 12 is a top plan view of a round cable closure with protectivetubes for the optical waveguides,

FIG. 13 is a cross-sectional view of a round closure with microcablespushed into the interior of the closure,

FIG. 14 is a cross-sectional view of a cylindrical cable closure whichhas been fitted into the road surface,

FIG. 15 is a cross-sectional view of a cylindrical cable closure, with aconcrete protective housing,

FIG. 16 is a cross-sectional view of a cable closure in a simpleconfiguration,

FIG. 17 is a cross-sectional view of an in-line closure which has beenbuilt into the road surface and the cover of which has a peripheralcollar,

FIG. 18 is a diagram of the arrangement of a closure for athrough-connection,

FIG. 19 diagrammatically shows an arrangement of the cable closure for aT-branch,

FIG. 20 is a diagram of the arrangement for a cross shaped branch,

FIG. 21 is a longitudinal cross-sectional view of an elongate cableclosure with diameter adaptations in the form of tubular adapter piecesor adaptation sleeves,

FIG. 22 is a longitudinal cross-sectional view of the cable closureaccording to the invention,

FIG. 23 is a cross-sectional view of a sealing head, in cross-section,

FIG. 24 is a transverse cross-sectional view of a splice arrangement inseries,

FIG. 25 is a transverse cross-sectional view of an arrangement ofoptical-fibre splices next to one another,

FIG. 26 is a cross-sectional view of a distribution or branch cableclosure,

FIG. 27 is a cross-sectional view of an assembly device for theinstallation of the cable closure,

FIG. 28 is a cross-sectional view of an arrangement for bringingtogether of the different optical waveguide transmission systems,

FIG. 29 is a cross-sectional view of an arrangement in a manhole in thefree earth,

FIG. 30 is a plan view of an open core hole with a laid-in elongationloop of a microcable,

FIG. 31 is a cross-sectional view of the inserted protective device,

FIG. 32 is a cross-sectional view of a cable closure which is accessiblefrom above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Represented in FIG. 1 is a slender, elongate cable closure according tothe invention, by which a connection of tubular minicables ormicrocables is made possible. The minicables or microcables comprise ineach case a pipe 8 or 10—here of the same diameter—in which the opticalwaveguides 11 are drawn in, blown in or laid in before the pipe joiningprocess. Within the cable closure 1, the optical waveguides 11 areconnected to one another by means of splices 26. The in-line cableclosure 1 comprises a tubular middle part 19 with end-face ends 16, onwhich external threads are arranged. The lead-in pipes 8 or 10 of theminicables or microcables are led in in a sealing manner with the aid ofsealing inserts 14 and/or cutting rings, and the necessary sealingpressure in the cable lead-in units is produced with the aid ofover-engaging union nuts 17, which have an internal thread 18 in eachcase at their free ends. The complete cable closure 1 is sunk below theroad surface 6 into the earth 7 or into cut-in laying channels. Since itconstitutes high mechanical protection for splices 26, it may also beused above ground, for example on masonry plaster.

Represented in FIG. 2 is an elongate in-line cable closure 2, in whichmicrocables 9 and 15 of different diameters are connected to each other.In this case, the same connecting and sealing technique as in the caseof the cable closure 1 according to FIG. 1 is used, and the onlydifference is that the lead-in diameters at the end faces of the cableclosure are different and are adapted to the respectively led-inmicrocable 9 and 15, respectively.

Shown in FIG. 3 in an in-line cable closure 1 a, the left-hand lead-inside of which corresponds to the exemplary embodiment according to FIG.1, while the right-hand lead-in side has a profiled

inlet spigot 4, onto which the continuing microcable 3 is fitted and iscorrespondingly sealed off. Th sealing may take place by adhesivebonding or crimping on of the microcable pipe on the lead-in spigot.This exemplary embodiment may be used in particular in the case of the“blown fibre” technique, in which optical waveguides are blown in at alater time in a laid hollow pipe. The hollow pipe 3 concerned, forexample of plastic, can be readily fitted onto the lead-in spigot 4 ofthe cable closure 1 a.

The exemplary embodiments shown in FIGS. 1 to 3 and 21 are suitable asstraightforward in-line cable closures, in which there are no excesslengths of optical waveguides, so that they are used as straightforwardrepair and connection links between the minicables or microcables.

Represented in FIG. 4 is a round, cylindrical cable closure 5, whichcan, for example, be sunk vertically into a core hole in the earth or inthe road structure. The cable lead-in units 37 are arranged tangentiallyat the wall of the closure so that the optical waveguides 24 of thefitted-on microcables 10 can be taken further along the inner wall 22 ofthe closure. In this way it is possible, for example, for the excesslengths of the optical waveguides to be deposited in an ordered way. Forrequired splices 26, the optical waveguides 24 are taken out from theexcess-length assembly and spliced. In doing so, it must be ensured thatbending in the splice depository does not go below the permissibleminimum bending radius 39 of the optical waveguides. The cylindricalinterior space 23 of the cable closure 5 may be separated intoappropriate compartments in a corresponding way for the individualfunctions, and the splices 26 are deposited in a horizontal plane in thecase of this exemplary embodiment.

FIG. 5 shows an exemplary embodiment for a cylindrical closure 5, inwhich the optical waveguide splices 26 are arranged vertically in thecylindrical closure space. Used for this purpose in this case are, forexample, sickle-shaped or arcuate segment splice organizers 32, whichcan be taken out vertically upwards for service work. The lead-inoptical waveguides 24 are deflected by means of indicated guides 25 suchthat it is not possible for bending to go below the minimum permissiblebending radii.

Represented in FIG. 6 is a cylindrical cable closure 5 for microcables,which is closed off towards the earth side in a hood shape and isaccessible from the surface 6 via a cover 20. The cover 20 can withstandhigh loading and closes off the cable closure 5 pressure-watertightly bymeans of a sealing system 21. In the case of this embodiment shown, thecable lead-in unit 13 is housed in the upper part of the closure, towhich the pipe 43 (FIG. 7) of the microcable is connected in apressure-tight manner, with the aid of an adaptation sleeve 87. Theoptical waveguides 11 are led in through this cable lead-in unit 13 anddeposited in excess lengths on a plurality of levels within the closurespace. Here, the excess lengths 30 of the led-in optical waveguides arestored in the upper deck 28 and the excess lengths 38 of the outgoingoptical waveguides are stored in the lower deck 28 a. The lead-throughs41 in the respective separating plates 29 make it possible for theoptical waveguides to be led through from one level to the other. Thelower region of the cable closure serves as splicing space 23, in whichthe splices 26 are fastened on removable splice organizers 32. Ifservice or splicing work is necessary, after removal of the cover 20 theexcess-length assemblies 30 and 38 are taken out, so that finally thesplice organizers can be removed. The hood-shaped termination of theinner wall 22 of the cable closure 5 is curved such that it can serve asa guide for the optical waveguides 31 leading to the splices. Themarking 25 is intended to indicate, that corresponding guides foroptical waveguides or optical waveguide groups can also be used in thesplicing space, allowing the clarity of the arrangement to be improved.The leading away of the optical waveguides into the connected pipe ofthe outgoing microcable takes place in turn via a cable lead-in unit 13,which is arranged here on the level of the storage space 28 a for theoutgoing optical waveguides 38. The sleeve-shaped cable lead-in units 13are drawn here diagrammatically as crimpable lead-throughs, butaccording to the special configuration provided by the invention the mayalso be fitted on tangentially, so that here too the advantagesdescribed above come to bear.

In FIG. 7 it is shown how the removal of the individual units from thecable closure 5 according to FIG. 6 proceeds for service work. Thus,first of all the excess lengths 30 of the incoming optical waveguidesand then the excess lengths 38 of the outgoing optical waveguides areremoved upwards, so that access to the splicing space, and consequentlyto the splice organizers 32 located there, is then free. As the arrow 42indicates, the splice organizers 32 can then be taken out upwards and bedeposited in corresponding splicers.

FIGS. 8 to 10 show basic units from which the cable closures accordingto the invention can be assembled. These basic units are let or placedinto corresponding core holes in the earth or road surface 6.

Advantageous in this case is the cylindrical shape of the closure, whichis closed off at one end by a flat base. As a result, under staticloading from above, the forces are distributed evenly over a largesurface area. Sinking into the road soil is not to be expected even whenthere in a high volume of traffic.

FIG. 8 shows a simple form of the cable closure 5, the cable lead-inunits 13 being arranged at different levels. As a result, differences inheight between the cable routes, as occur between road laying (about7-15 cm) and earth laying (about 70 cm), can be overcome. Thisembodiment comprises a single housing

of the interior space 23, which can be provided with the detailsdescribed above. Th cable lead-in units 13 may be sealed off, forexample, by sealing nipples, which are inserted at the point 37.

Presented in FIG. 9 is an exemplary embodiment which comprises aplurality of sections 33 and 35, which are arranged one above the other.Here, the cable lead-in units 13 and 36 are arranged in the separatingplane between the two sections 33 and 35, so that it is possible also tolead in uncut microcables or uncut optical waveguide conductors. Thismakes it possible to apply the splicing technique here. In the case of acable closure of cylindrical configuration, the sections 33 and 35 areindividual rings which contain suitable sealing systems in theseparating plane. A flat base 40 was chosen here as the termination.

FIG. 10 shows that a cylindrical cable closure can also be assembled,for example, from three individual sections or rings and it is possibleby turning the individual sections to alter the direction of the cablelead-in units 13. Thus, for example, with such a cable closure aright-angled branch can also be realized. Here too, correspondingsealing systems are used in the separating planes 34 between theindividual sections.

Shown in FIG. 11, likewise in a diagrammatic way, is the structuraldesign of a cylindrical cable closure 44, in which the cable lead-inunits 45 are led into the closure body tangentially in the form oftubular attachments. In this way, the optical waveguides can becontinued in the interior of the cable closure along the inner wall ofthe closure without the risk of buckling. Furthermore, it is shown thatthe cable lead-in units 46, which in the case of this example arelikewise led in tangentially, are provided with so-called compensationloops 47. These compensation loops 47 serve to compensate for tolerancesduring laying of the microcables and installation of the closures orelse to compensate for longitudinal movements in the case of differentcoefficients of thermal expansion. The diameter of these compensationloops is dimensioned such that in any event bending does not go belowthe minimum permissible bending radius of the optical waveguides, and ithas to be ensured that the compensation takes place without bucklingunder normal loading. It is also indicated in this diagram that, becauseof the excess lengths of optical waveguide 49, the splice organizer 48with corresponding splice reserve 50 can be taken out from the closurein the service position in direction 51. In protective tubes 54, theoptical waveguides are protected against mechanical loading inside andoutside the closure and ensure buckle-free handling, without bendinggoing below the minimum bending radius. The protective tubes 54 lead theoptical waveguides from the cable lead-in unit 45, 46 up to the spliceorganizer 48. The depositing of the cross-connection excess length 49 inthe interior space of the closure in the closed state is indicated bydashed lines. The connection to the microcables at the cable lead-inunits 45 and 46 is explained in more detail below. At the top right, anunused cable lead-in 45 is sealed off by a dummy plug 90. At the bottomright of the figure, a crimped connection 89 with respect to themicrocable 10 has been shown in principle.

In FIG. 12, a cylindrical cable closure 44 is sketched in a view fromabove, in which the cable lead-in units comprise microcablelead-throughs 56, through which the optical waveguides are led into theinterior of the cable closure. The lead-ins are in this case arrangedvirtually tangentially with respect to the inner wall of the housing,the free, outwardly pointing end being expanded in the shape of a nozzlein this representation, in order to be able to thread the opticalwaveguides into the flexible protective tube 54. These protective tubes54 are connected by fittings 55 onto the inner ends of the cable lead-inunits 56. For connection of the pipes 9 of the microcables, usually acrimp sleeve is used. Likewise, however, as shown here,

a shrink tube piece 57 may also be used. The optical waveguides of themicrocables are fed to the individual regions, for example the spliceorganizers 48, through the cable lead-in units and through the flexibleprotective tubes 54 via compensation loops 53. The transition may takeplace with the so-called maxibundle adapter. Consequently, if required,optical waveguides may be divided between a plurality of protectivepipes. There is also the possibility of dividing the optical waveguideswithin the splice organizers 52 between a plurality of organizers 48.For this purpose, the optical waveguides are led through the bottom ofthe organizers 48.

FIG. 13 shows in a diagram an in-line cable closure built into the roadsurface, in a view from above. In this way, the individual microcables 9can also be pushed into the interior of the closure. The tension reliefand the sealing likewise take place by crimping at the points 58. It isalso possible to use, however, as shown here in the left-hand half ofthe figure, an additional shrink tube 59 or a permanently elasticannular seal, with the aid of which the sealing with respect to thecable lead-in unit 56 takes place. Furthermore, sealing could also takeplace in the interior of the cable closure 44, at the end of thelead-through, with corresponding sealing means 60. Suitable for thispurpose is, for example, an annular lip seal 60, which is shown inprinciple as a shaft-sealing ring in the right-hand half of the figure.

Shown in FIG. 14 is an in-line cable closure 61 which is built into theroad surface 6 and is fitted in a metallic protective housing 64 suchthat it is protected against mechanical loads. A cast iron cover 68 iscaptively fastened by a pivot bolt 67 to the protective housing 64. Theprotective housing 64 has an opening 63 in the wall for leading in themicrocables 62. The protective housing 64 is embedded in concrete 65,which is in a lower region of the core hole which is formed in the roadsurface 6, in order to prevent sinking. The remaining annular gap isclosed with hot bitumen or 2-component casting compound 65 a. The cover68 is slightly counter-sunk with respect to the carriageway surfacingand is accessible at any time for service work. The sealing cover 73 isdescribed further below. The protective housing 64 and the cable closure61 are arranged concentrically with respect to each other, it beingpossible for the intermediate space to be provided with a flexible foamfilling 66.

FIG. 15 illustrates a sketch of an in-line cable closure built into theroad surface 6 and having a concrete protective housing 71, whichprotects the in-line cable closure against mechanical loads. Such aprotective housing of precast concrete is suitable in particular forsinking into a paved road surface. Here too, a cover 74 which canwithstand high loads is provided, which cover is let into a ring 75.Here too, a pivot bolt 67 is provided. The cable lead-in units 70 arenot flexible here and, because of the microcables 62, have to be ledinto the cable closure 72 rectilinearly. The cable sealing takes placeoutside the concrete protective housing 71 by crimping 58 (left-handside) or with the aid of a shrink tube piece 69 (right-hand side). Anycompensation loops must be situated outside the concrete protectivehousing 71 and are not shown here. The cable closure 72 is closedupwardly, underneath the load-withstanding cover 74, by a sealing cover73. The latter seals off the closure space downwardly by an O-ring 91.In this diagram, the sealing cover 73 is secured and fixed, for example,by an annular screw.

FIG. 16 illustrates in a diagram an in-line cable closure 72 built intothe road surface 6, and this is a simple mechanical cable closure formicrocables. For reasons of overall clarity, the cable lead-in unitsalready explained above have not been shown. The cast cover 76 absorbsthe mechanical loads and leads them directly into the closure housing72. The cast cover 76 is provided with a centering groove 77, whichensures non-slip support. For the guidance

of the cast cover 76, hinged devices 67 and 78 are provided at thesides, by which devices adequate, positioning is ensured. The cableclosure 72 is in turn separately sealed off upwards, underneath the castcover 76, by a sealtight cover 73. The sealing takes place, for example,by an O-ring 91. The cover 73 is fixed in this diagram by securingwedges or securing pins 92, which provide adequate cover-pressing ontothe O-ring.

Shown in FIG. 17 is a cable closure 72, which corresponds to that fromFIG. 16, the load-bearing cover 80 here having a peripheral collar 81.By this peripheral collar 81, the cast cover 80 is fixed adequatelyagainst shifting on the peripheral wall 79 of the cable closure 72. Thecover 73 is in this case fixed by a snap ring (Seeger circlip), whichlocks into an annular groove. Opening takes place by means of specialpliers. The closure is secured against unauthorized access.

FIG. 18 illustrates in a diagram the conditions in the case of athrough-connection of microcables 84, which are connected via connectionunits 82 and compensation loops 47 to the cable lead-in units of thecable closures 44. To reduce the variety of types, the closures areprovided, as standard as far as possible, with 4 cable lead-in units. Ifnot all the cable lead-ins are required, unoccupied cable lead-ins canbe closed off pressure-watertightly by dummy plugs.

FIG. 19, on the other hand, illustrates the principle in the case of aT-branch of microcables 84. Here, likewise two of the microcables 84 areled into the cable closure 44 in the way described above, a furthermicrocable 84 being led out, perpendicularly with respect to this firstrouting, tangentially from the cable closure 44. In this case, thebranched-off microcable 84 is led in via a cable lead-in unit 83directly without a compensation loop. The compensation loop 47 has

in this case been provided on the cable end of the microcable 84. Unusedcable lead-ins are closed pressure-water tightly by a dummy plug.

Sketched in FIG. 20 is a cross-shaped branch, in which the basicprinciples shown in FIGS. 18 and 19 are applied. In this case, it may beexpedient for the compensation loops for the branching-off microcables84 to be pulled up in a bow shape, as is indicated at the point 85.Compensation loops 47 are provided directly at the microcable ends.

It can be seen from the diagrammatically illustrated basic principles inFIGS. 18, 19 and 20 that a cylindrical cable closure according to theinvention is particularly advantageous for the laying of minicables ormicrocables. On account of the possibility of tangentially leading inthe relatively rigid pipes of the microcables, changes in direction inthe routing can be arranged without any problems.

Depicted in FIG. 21 is a variant of the slender in-line cable closure 1b. In the case of this closure, the led-in pipes 8 and 10 arepermanently fixed by plastic crimping of a softer metal. For thispurpose, adapter pieces 87 of soft metal are crimped onto the pipe endspressure-watertightly and permanently. An outer pipe 88, which iscrimped onto the adapter pieces 87 at both ends, protects the splices26. The inner bore of the adapter pieces 87 can be matched to theexternal diameter of the respective microcable 8 or 10.

The compensation loops 47 may be provided both at the cable lead-ins orcable lead-in units and directly at the ends of the microcables.

The cable lead-in units of the cable closure may also be designed asflange units, plug units inserted in a sealtight manner

being provided for the connections of the optical waveguides. Theoptical waveguides are likewise provided with plug units, so thatconnection without any problems can take place, the ends of theminicables or microcables being provided with adapted flange units forsealtight coupling.

Furthermore, the complete cable closure, comprising closure body, cover,splice organizer, protective tube for excess lengths of opticalwaveguides, cable lead-in units, sealing systems, crimp connections andcompensation loops, may be prefabricated in the factory.

A development of the invention is based on the object of providingslender in-line or vault cable closures for microcables, the diameter ofwhich closures is only slightly greater than the diameter of themicrocable and in which closure the microcable inlets can be sealed offby simple sealing methods. The object set is achieved with a cableclosure of the type explained at the beginning by sealing heads ofdeformable material, preferably of a metal, being crimped onto the pipesof the optical-fibre cables in a sealing manner at peripheral crimpingpoints, by the closure pipe likewise consisting of deformable material,preferably of a metal, and being crimped on at its and faces onto thesealing heads at peripheral crimping points and by the closure pipebeing dimensioned in length such that adequate excess lengths of opticalwaveguide can be arranged in waveform extent and optical-fibre splicescan be arranged.

It is furthermore the object of a development of the invention that,with such an in-line or vault cable closure, a sealtight spliceconnection is produced.

The slender in-line cable closure according to the invention for themicrocables described essentially comprise a two sealing heads and aclosure pipe. The sealing heads are interchangeably

graduated and optimized in their internal diameter for the differentmicrocable diameters. The connection between the sealing heads and theend of the pipe of the microcable takes place by a crimping operation.In this operation, the soft material, in particular metal, of theconcentric sealing head is permanently deformed and pressed onto thepipe of the microcable in a sealtight manner. To increase the sealingeffect, the sealing heads may be provided with peripheral grooves in thecrimping regions. The same effect can also be achieved if a plurality ofcrimpings are carried out in series one behind the other. Within thecable closure, thus a plurality of splices may be deposited together inone multi-fibre shrink splice protector. By exposure to heat, a sealingof the splices is created. For splicing, multi-fibre splicers known perse may be used, such as for example the splicer X120 from the RXScompany. However, conventional thermal splicers may also be used forindividual fibres, for example the device X75 from the RXS company. Toavoid crossovers and loopings of the splices in the splice protector,the individual optical waveguides must be fixed on both sides of thesplice protector by an adhesive tape. Preferably, a parallel alignmentof the individual optical waveguides and their fastening takes place ina planar mounting for optical waveguides, such as are known perese.Finally, all the splices are to be sealed together with a spliceprotector. In cases of few fibres, a plurality of crimping spliceprotection parts may be used instead of the multi-fibre spliceprotector. The splices may be arranged in series one behind the other orelse next to one another in the cable closure. In order that the closurepipe can be pushed over the splices without damaging the opticalwaveguides, the optical waveguides must be brought up to the splices, sothat fastening to the splices is recommendable. The splicing operationis expediently performed on a workbench, on which the optical waveguideends to be spliced are clamped in dividable fastenings. After thesplicing operation, the splicer is removed again, for example loweredinto the workbench. Subsequently, the respective sealing head is pushedonto each pipe and of the microcables and is fixed in a sealing mannerover the entire periphery by crimping. For further assembly, one of themicrocable fastenings is then removed and the closure pipe is pushedwith the aid of a guide over the splices until the second sealing headis taken up by the closure pipe. The required excess length of opticalwaveguide within the closure is then achieved by displacing at least oneclosure head. For this purpose, the fastenings of the pipe ends of themicrocables have to be displaced. Thereafter, both ends of the closurepipe are crimped by a crimping device, for example crimping pliers,radially onto the sealing heads. All the operations in the assemblydevice are provided with longitudinal stops, or at least visualmarkings, for reasons of better reproducibility.

Dividing optical waveguides between different branching cables can beachieved with specially designed sealing heads which are provided with aplurality of cable lead-throughs. The fixing and sealing at these cablelead-throughs, which takes place with cable lead-in spigots, isperformed outside the cable closure by crimping. Alternatively, it ispossible to dispense with crimping between the closure pipe and theclosure head if, instead, the two parts are screwed to each other orfixed in a sealing manner by a shrink tube.

If required, the interior space in the cable closure may also be filledwith filling compound. For this purpose, the closure pipe is providedwith filling holes, which are closed for example by clamping rings or bya hot- or cold-shrink tube.

Thus, with a structural design according to the invention, the followingadvantages are obtained in comparison with the existing prior art.

It is a slender, no longer openable cable closure of plasticallydeformable metal.

The closure is stable with respect to transverse compressive stress,tension-resistant, torsionally rigid and pressure-watertight.

Assembly of the cable closure, comprising few individual parts, is quickand easy.

The metallic seals are pressure-watertight seals which are resistant totemperature and aging at the same time.

The sealing does not involve any plastic or rubber seals, so that noflowing of materials occurs.

Only a few, annular and concentric seals with a large sealing surfacearea are used.

There are no longitudinal seals.

A permanent, pressure-watertight optical-fibre cable/sealing headconnection which is stable with respect to tensile, compressive andtorsional forces is produced by crimping.

A permanent, pressure-watertight sealing head/closure pipe connection isproduced by crimping.

The sealing heads consist, for example, of plastically deformable metal,

 for example copper, aluminium.

Simple standard crimping pliers which have appropriate inserts and carryout the deformation plastically are adequate for the crimping operation.

A plurality of crimpings in series one behind the other increase thesealtightness and pull-out force of the microcable ends.

The sealing effect can be increased by peripheral grooves on the sealinghead.

On account of the small diameter, the cable closure may be laid in theaxial direction of the microcables, so that a widening of the layingchannel is adequate, the laying depth of the microcable likewise beingadequate.

The metallic closure pipe and the metallic sealing heads provideelectrical through-connection of the microcable.

The crimping of ductile copper microcables and of hard, resilient steeltubes is possible.

The cable closure in resistant to buckling and, consequently ensuresthat optical waveguide bending radii are maintained during laying.

The sealing heads of the cable closure of different internal diameterare interchangeable, but have the same external diameters.

The closure heads have in the longitudinal bore a length stop for themicrocable, so that penetration of the microcable into the interior ofthe cable closure is prevented. The bores of the closure heads arebevelled and facilitate assembly during leading in of the microcables.

This structural design provides a standard size of closure for alldiameters of possible microcables.

Due to the interchangeability of the sealing heads, connectingmicrocables of different external diameters is also possible.

Microcables with a low number of optical waveguides and with a highnumber of

optical waveguides can be spliced with one another.

A shrink splice protector allows a plurality of optical-fibre splices tobe protected.

Both individual optical waveguides and optical waveguide strips can beaccommodated in the closure.

Depending on the width of the closure pipe, the optical-fibre splicescan be arranged in series one behind the other or else next to oneanother.

Standard tools can be used for the splicing, such as a splice protectorand thermal splicer for optical waveguides.

The length of the closure allows excess lengths of optical waveguide tobe accommodated adequately on both sides of the optical-fibre splices.

The optical-fibre splices are freely movable within the cable closure.

The following can be used, for example, as deformable materials: copper,copper-based wrought alloys, aluminium, cold-workable aluminium alloysor plastically deformable, non-hardened, stainless steel.

Furthermore, the sealing between the sealing-head outer casing and theclosure pipe and/or between the sealing-head bore and the pipe end ofthe microcable may alternatively also take place by a cutting-clampingconnection, as is known perese from sanitary installation engineering.The cutting rings used for this purpose are plastically deformed byunion nuts and thereby seal off the concentric, tubular closure partsfrom one another. For this purpose, however, internal

and external threads have to be provided an corresponding sealing heads.

In FIG. 22, a slender cable closure KM is represented in longitudinalsection as an in-line closure for two microcables MK1 and MK2 withprotective splices SS lying in series one behind the other in theinterior of the cable closure KM. A plurality of individualoptical-fibre splices are brought together and protected together in amultiple splice protector SS. On both sides of the protective splices SSthere is adequate free pipe length in order to accommodate the excesslength of optical waveguide LU1 and LU2, respectively. The protectivesplices SS are freely movable within the cable closure KM. The ends ofthe pipes of the microcables MK1 and MK2 are fixed in a sealtight mannerby crimping at the crimping points KRK of the two sealing heads DK1 andDK2, the required tensional, torsional and compressive strength beingachieved at the same time. The closure pipe MR1 pushed over the twosealing heads is crimped onto the two sealing heads DK1 and DK2 andclosed in a pressure-watertight manner on both sides at the crimpingpoints KRM. The individual optical waveguides are fixed with the aid offixings F in the region of the protective splices to the latter in orderto facilitate the assembly of the closure pipe MR1. In this case, theends MKE1 and MKE2 of the pipes of the microcables MK1 and MK2,respectively, are led through the respective sealing head DK1 or DK2into the interior of the closure.

Represented in FIG. 23 is a sealing head DK, which has an inner boreBDK, the diameter of which is matched to the microcable to berespectively fed in. At the inner end of this bore BDK there is a stopAS for the led-in cable. At the inlet of the bore BDK, the edge of thebore is provided with a bevel AF, in order to facilitate the leading inof the microcable. On the outer surface of the sealing head DK,peripheral sealing grooves may be arranged, by which the sealing effectis improved.

FIG. 24 shows a cross-section through the cable closure in the spliceregion of the closure pipe MR1. Within a protective splice SS, of whicha plurality are arranged in series one behind the other in thisexemplary embodiment, there are a plurality of optical waveguide splicesLS, which are fixed next to one another. Such a splice protector is,finally, also provided with a fixing F, by which the excess lengths ofoptical waveguide LU led past the splice 55 are loosely held in theclosure space.

FIG. 25 illustrates that a plurality of splice protection units SS, withthe optical-fibre splices LS contained therein, may be arranged next toone another, although then the cross-section of the closure pipe MR2 hasto be greater than in the case of the exemplary embodiment according toFIG. 22.

In FIG. 26, the cable closure KM is designed as a branch cable closure,two sealing heads DK3 and DK4 are used and the closure pipe MR2 iscrimped in a secure and sealtight manner at the crimping points onto theheads DK3 and DK4. In the case of this exemplary embodiment, there areadditionally provided filling openings EF, which can be closed with theaid of sealing tapes DB. Arranged in the sealing heads DK3 and DK4 arecable lead-in spigots KES1 to KES4, which correspond to the sealingheads DK1 and DK2 of the previously described in-line cable closure,that is to say they too are of plastically deformable material and servefor the sealtight connection of the microcables MK3 to MK6. At thecrimping points KRK of the cable lead-in spigots KES1-KES4, insertedinto the lead-in bores EB of the sealing head DK3 and DK4, respectively,the mechanical supporting and sealing off of the led-in microcablesMK3-MK6 takes place. Contained in the interior of the cable closure arethe protective splices BS, in which the individual optical-fibre splicesare accommodated in groups.

FIG. 27 finally shows an assembly arrangement for the assembly of thecable closure according to the invention once the

splicing work has bean carried out with the aid of a splicer SPG. Onboth sides of the splicer SPG there are removable fixings FMK1 and FMK2,respectively, for the fixing of the respective microcables MK1 and MR2to be connected. The sealing heads DK1 and DK2 of the cable closure tobe assembled are pushed onto the ends of the microcables MK1 and MK2,respectively, and fixed by crimping. Beforehand, however, the closurepipe MK1 has been pushed over the microcable MK1 and fixed. Once thesplicing work with the aid of the splicer SPG has then been completed,the fixing FMK1 at the sealing head DK1 is released and removed. As aresult, the closure pipe MR1 previously pushed on and fixed for assemblycan be pushed in the direction of the indicated arrow PFMR over the twosealing bodies DK1 and DK2. By corresponding displacement of the sealingbodies DK1 and DK2, respectively, the excess lengths LU1 and LU2contained in the interior can then be formed. Subsequently, the closurepipe MR1 is fixed in a sealing manner onto the sealing heads DK1 and DK2by crimping.

The invention relates to a method of connecting a microcable comprisinga pipe with led-in optical waveguides, which has been introduced into alaying channel in solid laying ground, to an existing optical-fibretransmission system of a conventional type.

Optical-fibre transmission systems comprising optical-fibre cables knownperese are sufficiently known and already laid, subsections beingcoupled together by the conventional connection units. However, theoptical-fibre transmission system comprising tubular microcables, whichcomprise homogeneous and pressure-watertight pipes into which opticalwaveguides are introduced, cannot be connected in the previouslycustomary way to an existing optical waveguide system, since themicrocables differ considerably in structural design and in the type oflaying from the conventional optical-fibre cables.

Furthermore, it is the object of a development of the invention to findmethods of connecting a microcable with the aid of cable closures of thetype described to conventional optical-fibre transmission systems, itbeing intended for the connection to take place in the same layingground or in laying grounds of different types of construction. Theobject set is then achieved with the aid of a method of the typeexplained at the beginning, when joining together in the same layingground with cable closures, by the microcable being led into an adapterclosure, for receiving microcables, through a cable lead-in of a manholeof the existing optical-fibre transmission system which has been made inthe same laying ground, by optical waveguides of a flexiblecross-connecting cable being spliced onto the optical waveguides of themicrocable within the adapter closure and by the cross-connecting cablebeing led into a conventional splicing closure for optical waveguidesfor connection to the optical cables of the existing optical-fibretransmission system, the joining together being performed within thesplicing closure.

Furthermore, the object set is also achieved with the aid of a method ofthe type explained at the beginning, when joining together in differentlaying grounds, by the microcable being led at the end of the solidlaying ground into an adapter closure at the height of the layingchannel and spliced onto a buried cable, by the buried cable being laidin the earth at the height of the leading-in level of the manhole madein the earth, led into the manhole and spliced there within a splicingclosure onto the existing optical-fibre network.

With the aid of the method according to the development of theinvention, it is then possible to couple an optical-fibre transmissionsystem made up of microcables to an optical-fibre transmission systemwith conventional optical-fibre cables. The coupling of tubularmicrocables

onto the existing network in this case takes place with cable closuresof which the cable lead-ins are designed for the requirements of themicrocables. Used for this purpose are cable closures of metal of whichthe spigot-shaped cable inlets are crimped onto the pipes of themicrocables. This method in not possible with the aid of conventionalcable closures. From such an adapter closure, a cross-connecting cableof a conventional type is then led to a conventional splicing closure,into which the conventional optical-fibre cables are also led in. There,the splicing of the optical waveguides of the microcable, or of thecross-connecting cable, with the optical waveguides of the conventionaloptical cables is performed. This has the advantage that the tubularmicrocable ends in a special adapter closure, from which a flexibleoptical-fibre cable in led into a conventional splicing closure, whereany service work can then be performed. In this case, the microcable,which is susceptible to buckling, can be rigidly fixed on the manholewall, so that any buckling of the pipe can be ruled out. In theconventional splicing closure, on the other hand, cross-connectingexcess lengths of fibres for subsequent splicing and all the splices canbe accommodated. In the adapter closure itself, only the microcable isaccommodated and connected to the flexible cross-connecting cable.

If a special adapter closure cannot be used, the microcable must be leddirectly into the splicing closure by special measures, correspondingprotective measures having to be taken for the pipe which is susceptibleto buckling. Suitable for this purpose is, for example, a tube which isstable with respect to transverse compressive stress and protects themetal pipe of the microcable against buckling and damage. The protectivetube also makes the microcable much thicker, so that it can beidentified better in the manhole.

Access to an already existing manhole, in which optical cables of aconventional type have already been led in, is achieved by the layingchannel in which the microcable

is laid being cut into the solid laying ground in the direct vicinity ofthe manhole. The normal laying depth of such a route is 70 to 150 mm.From the road surface, a core hole is then made up to the route of themicrocable on the outer wall of the manhole. Subsequently, the manholewall is drilled through in the upper manhole region and the microcablein led in from outside. The core hole made outside the manhole in thiscame serves as a leading-in aid, to compensate for laying inaccuraciesand for receiving the loop of excess length of cable of the microcableas well as for sealing off the manhole from the outside. The manhole issealed off by a conventional masonry lead-through, such as for examplewith lead-through seals known peruse for manholes. In the interior ofthe manhole, the microcable is then led horizontally along the manholewall up to the adapter closure.

If the manhole for the conventional optical-fibre systems is not made inthe solid laying ground in which the microcable runs, difficulties arisein bringing the microcable up to the manhole; this is because therelatively rigid microcable could, for example, be sheared off. In suchcases, there is then placed at the end of the laying channel in thesolid laying ground, for example of a road surfacing, an adapterclosure, into which the microcable is led. Here there is then spliced ona flexible buried cable, which in laid at a deeper laying level in theearth up to the leading in of the manhole. Here, the splicing onto theexisting network then takes place in a splicing closure.

The leading into a manhole also open up the possibility that microcableslaid at different heights can be brought together.

The following special features and advantages of the method are obtainedaccording to the invention:

The customary optical waveguide assembly technique can be retained.

The bringing together of the new and old optical-fibre systems can takeplace in already conventional optical waveguide accessories.

The small laying depth of the microcable allows the existing free spacein the upper manhole region also to be used.

A core hole on the outer wall of the manhole suffices for leading in themicrocable, so that no excavation of the surrounding earth is necessary.

In such a way, routes having different laying heights can be broughttogether.

The manhole 103 shown in FIG. 28, which is arranged below the roadsurface 101 of the laying ground 102 and is covered by a cover 114,contains first of all an optical-fibre transmission system 104comprising conventional optical-fibre cables. Already provided in thissystem is a conventional splicing closure 113, excess lengths 112 ofoptical-fibre cable introduced in the customary way allowing a certainmobility of the splicing closure for splicing work. These optical cablesof the conventional system 104 are usually in ducts and are led in vialead-in seals 106 relatively deep in the lower region of the manhole. Bycontrast, the newly added microcable 105, comprising a pipe and opticalwaveguides guided therein, in led into the manhole 103 via a cablelead-in 107 in the upper region of the manhole, since the laying channelhas only a depth of 70 to 150 mm. For this purpose, a core hole 108 isintroduced outside the manhole 103, in order to have sufficient freespace for leading in the microcable.

Into this core hole 108 there may also be introduced, for example, atubular excess length of the microcable 105, with which it is possibleto compensate for tolerances in length. After introducing the microcable105, the laying channel is filled with a filling compound 115, such asfor example bitumen. Within the manhole 103, the led-in microcable 105is initially mechanically protected and supported with the aid of aprotective tube or protective pipe 109 and is subsequently led into anadapter closure 110, which in suitable for the leading in ofmicrocables. In this adapter closure 110, the optical waveguides areconnected to a flexible cross-connecting cable 111. After leaving theadapter closure 110, this flexible cross-connecting cable 111 is thenled into the splicing closure 113 of the already existing optical-fibretransmission system and coupled to it via optical-fibre splices. Theflexible cross-connecting cable 111 is also deposited in the manholewith corresponding excess lengths 112, so that, even after thecross-connecting cable has been led in, removal of the splicing closure113 from the shaft for service work is possible.

FIG. 29 shows an exemplary embodiment of the, procedure when the manholeis not in the region of the solid laying ground in which the microcableis laid, but is in the neighboring, relatively soft earth. Therelatively rigid microcable could be damaged in the transitional region.Thus, if the manhole 103 is in the, earth 123, the microcable 117 can belaid only up to the end of the solid laying ground, for example thecarriageway 116. Prom there, a buried cable 124 has to be led to thecable lead-through 125 of the manhole. The standard laying depth isabout 60 to 70 cm in the earth. The difference in height can be overcomewith an adapter closure 120. The microcable 117 is led in and sealed offin the upper region by the lead-in 118. The buried cable 124 is ledthrough a spigot 121 and sealed off, for example by a shrink tube piece122. For leading into the manhole 103, the buried cable 124 has to beburied in the ground and the out rewall of the manhole 103 has to beexposed. Within the manhole 103, the buried cable in then led into thesplicing closure installed there, where the optical waveguides areconnected.

During the laying of microcables, which comprise a pipe and opticalwaveguides loosely introduced therein, it is necessary to arrange excesslengths of cable before branches, closures or after relatively longsections of cable, in order to make required compensations of lengthspossible. Such settlements, elongations and also temperature-inducedchanges in length during the interaction of materials with differentcoefficients of thermal expansion are compensated by so-calledelongation loops. During laying in laying channels which are made insolid laying ground, these elongation loops have until now been madevertically in correspondingly sunken laying channels, perpendicularlywith respect to the surface of the laying ground. This leads todifficulties, however, if the laying ground, such as for example acarriageway surfacing, is not sufficiently thick.

A further object of the invention is thus to provide a protective devicefor terminating core holes in which the elongation loops of microcablesare horizontally laid. The object set is achieved with a protectivedevice of the type explained at the beginning by the said devicecomprising a protective cover and a driving-in peg, provided centrallyat one end, for fixing in a central hole at the bottom of the core hole,by the diameter of the protective cover corresponding to the diameter ofthe core hole and by filling material being arranged above theprotective cover for sealtight termination and for filling the remainingcore hole.

The advantage of protective devices according to the invention is thatelongation loops of microcables can be horizontally laid reformed intocore

holes which have a diameter which corresponds at least to the minimumpermissible bending radius of a microcable, since the possiblemechanical loading is absorbed by it and since such a termination alsohas the necessary sealtightness. Furthermore, it is of advantage thatnow the core holes are only required to be of a small depth, so thatbreaking through the solid laying ground, such as for example thesubgrade of a carriageway, can no longer occur. Such an intervention tothe mechanics of the solid laying ground, for example a road surfacing,is consequently uncritical. The required diameter for such a core holeis of the order of magnitude of 150 mm, so that these core holes canstill be made with conventional machine tools without any problem.Consequently, the same tool can be used to produce core holes forelongation loops, cable branches or setting holes for cylindrical cableclosures, as are customary in the use of microcables.

The protective device according to the invention comprises a more orless mushroom-shaped mounting, which is inserted into the core hole ofthe solid laying ground and upwardly covers the latter such that theoriginal strength of the laying ground, for example the surfacing forroad traffic, is restored. Within the core hole, the coiled-up excesslength or elongation loop of the microcable in held down. In addition,the core hole is sealed off with respect to the surface of the solidlaying ground and the microcable is protected against mechanical loadingfrom above. This problem in particularly important if, due to elevatedclimatic conditions, for example in the case of a temperature rise above30° C., the bitumen of the road surfacing softens and the mechanicalload-bearing capability is reduced. For example, in high summer, even inour temperate zones, temperatures of over 60° C. are measured in theasphalt. The hollow space of the core hole, in which the elongation loopis located, may be filled with a filling material,

which must not, however, restrict the, mobility of the microcable. Theprotective device upwardly terminates the core hole and the region thereabove is sealed with hot bitumen. Additions of solid material such aschippings increase the strength of the cast bitumen, so that in this waysomething approaching the strength of the asphalt is achieved.

Represented in FIG. 30 is, a core hole RB in solid laying ground VG, inwhich two laying channels VN1 and VN2 run in tangentially. The core holeKB has a diameter which is adequate for receiving the excess length orelongation loop DS of a microcable MK in a horizontal position for therange of elongation to be expected. A central hole ZB serves forreceiving and arresting the protective device according to theinvention. The hollow space of the core hole KB may, if required, befilled with a filler, which must not, however, significantly influencethe mobility of the elongation loop DS. The laying channels may be ledinto the core hole at different angles of offset, so that virtually anyangling off can be carried out for the further running of a layingroute. In addition to the central hole ZB, further holes may be made inthe laying ground, serving for example as an outflow for condensed waterin the core hole KR or one of the laying channels VN1 or VN2. Whenlaying in the elongation loop DS, it must be ensured that the microcableMK does not touch the wall of the core hole, so that during anyelongation the laid-in microcable can also give way outwards.Consequently, compressive stresses in the microcable are reduced withoutcompression occurring and without risking buckling. When shortening themicrocable, the elongation loop may be pulled together without the cablebeing subjected to tensile stress. In this figure, a deflection of themicrocable MK of 90° is shown and the excess length or elongation loopDS is then stored in a 450° loop. Such an arrangement may be used inrespective of the inlet or outlet angles for deflecting a route or

else as an ancillary means ahead of a following cable closure.

FIG. 31 shows in a sectional representation through the core hole KB theposition of the elongation loop DS of a microcable MK and themushroom-shaped protective device, which comprises the protective coverSD and a driving-in peg ES, which has, for example, in the region of theelongation loop DS a minimum diameter limitation ESB of a diameter whichcorresponds to the minimum permissible bending radius of the led-incable MK. In this way, there is no risk that the microcable MK could beexcessively beat or buckled. The free space above the protective coverSD is filled with a filler FM, preferably a hot bitumen, whereby asealing of the core hole KB takes place. If hot bitumen is used, amixture with chippings SP is expedient, since in this way an adaptationto the road surfacing SO can be achieved. Furthermore, it is shown inthis FIG. 31 that a pulling eyelet ZO may be provided for lifting theprotective cover SD. The protective device according to the inventionmay, however, also be of a multipart configuration, the driving-in pegES then expediently having in the upward direction a receiving pin AS,onto which the protective cover SD can be placed or screwed. Thediameter limitation ESB lying thereunder in this case form a peripheralrest for the protective cover SD. The diameter limitation ESB may alsobe fitted on as an extra part in the form of a sleeve. With thedriving-in peg ES, the entire device is fixed in a central hole in thelaying ground within the core hole KB by driving in.

To sum up, further special advantages of the protective device arelisted:

It is a temperature-independent protective device for core holes, sincethe protective cover compensates for the differences in heat in theasphalt and dissipates the heat via the peg

into the earth. As a result, there is also no settling or flowing of theasphalt above the protective cover.

The elongation loop of the microcable can move freely underneath theprotective cover, to be precise even if loose fillers, such as stonechips, bitumen, prefabricated profiles of polystyrene or one-componentfoam, are filled in. Consequently, the hollow space is largely protectedagainst the formation of condensed water, since a seepage of anycondensed water occurring is also ensured by additional holes in thecore hole, which reach into the frost blanket of the laying ground.

The protective cover absorbs the loading from above and directs it viathe driving-in peg into the solid laying ground. As a result, highpermanent loading is possible without subsidence. The same applies inthe case of high area loading or else in the case of puncti-formloading, as may be caused by tyres of vehicles or by sharp objects suchas props, tools, chisels, knives, pins or stiletto heels.

If a large elongation length is required, a correspondingly large corehole may be made, it being possible for the radii of the elongationloops to be formed simply and without a tool. Buckling is in this casescarcely possible.

The surface of the protective cover may be roughened, in order thatbetter adhesion with respect to the cast material is achieved.

It is also ensured by the protective cover that the elongation loop doesnot spill out or move out upwards when an elongation operation isproceeding.

The filling of the hollow space of the core hole above the protectivecover ensures that, when the road surfacing to renewed, only the fillerabove the protective cover

is cut away and renewed, so that the protective device remainsunaffected by this.

A further object of the invention is to provide a cable closure foroptical waveguides which is fitted in solid laying ground, is accessiblefrom above and has leading-in possibilities for deeply laid cables. Theset of objects is then achieved with the aid of a cable closure of thetype explained at the beginning, by the cable closure comprising anouter body which can withstand high mechanical loads and a cable-closuresealing body fitted in the outer body, by the outer body having aremovable outer cover, which is at the same height as the surface of thelaying ground, by the cable-closure sealing body lying thereunder beingclosed off by an upwardly removable sealing cover, by cable connectionunits in pipe form being led in from below through the outer body intothe cable-closure sealing body and by the ends of the cables being ledinto these cable connection units and sealed off.

The cable closure according to the invention is an upwardly accessibleclosure, making it possible for splicing and cross-connecting work andalso lining up of fibres or twin copper wires to be performed withoutexposing the closure. Until now, fibres and twin copper wires of localand connecting cables have been accessible only if the entire closure isexposed and the closure body is removed. At the same time, the closuresare usually at the same laying height as the cables. Digging work is,however, usually laborious, so that much time is additionally taken upfor the repair and service work to be carried out. In the case of thework to be performed according to the invention, there is no need fordigging work, since the upper side of the closure terminates flush withthe surface of the laying ground. Such a closure is suitable inparticular for leading in microcables, which are arranged at arelatively small depth in laying channels of solid laying ground. Inaddition, in the case of the cable closure according to the invention,there is also the possibility of leading in standard buried cables,which usually run at a greater laying depth. Provided for this purposearm cable connection units, which are led into the cable closure frombelow, the leading-in height of these cable connection units beingadapted to the laying height of the buried cables. In this way, evendeeper laid buried cables can be reached from the surface of the layingground without special measures, such as digging work, being necessary.

Such cable closures may be used as branch cable, closures and/or in-linecable closures in local and branching networks. This is particularlyfavourable, since switching and cross-connecting work is recurrentlynecessary in the local network. On account of the simple structuraldesign of the cable closure according to the invention, it may be usedin an uncomplicated way in footpaths, pavements and cycle paths, inparticular in urban areas. All that is required for this purpose arepaved squares, roads or paths, the load-withstanding cover simply havingto be removed for access to the cable closure, in order to gain accessto the fibres or twin wires from the surface. If the cable closureaccording to the invention is used, special advantages with respect tosystematic utilization of the existing infrastructure are then obtainedon account of the compact structural design and the good accessibility.

In the configuration according to the invention, the mechanical loadsare absorbed by the outer body, which preferably consists of grey castiron, while the cable-closure sealing body in the interior of this outerbody can be closed in a sealtight manner and contains the individualcommunication parts. The sealing cover and the outer cover areexpediently secured against unauthorized opening and, if appropriate,can be locked. Overall, the outer body can withstand high mechanicalloads up to a bridge class of 30 and more, so that the cabs-closuresealing body has to meet only the conditions with respect tosealtightness. The hollow space between the outer body and thecable-closure sealing body may expediently be filled or plugged with afiller, so that the two bodies are connected to each other in a dirt-and watertight manner as a unit. The closure sealing body ispressure-watertight and can be sealed off well and consists of plastic,diecast materials or metal. For fastening, there is preferably provideda sealing cover, the fastening mechanism of which is designed as aturn-lock or bayonet fastener. Such a closure may also be built at alater time into existing routes of pavements and cycle paths, since thedesign means that it can fit in well with the local conditions. Thestructural design of the cable closure also allows further cables to beled in at a in later time if cable connection units were additionallyprovided at the beginning. For easy identification, the cable closurecan, because of its easy accessibility, be easily assigned by labellingor coding, so that there is no need for laborious search andcoordination measures.

FIG. 32 shows the upwardly accessible cable closure KMO according to theinvention, which comprises the outer body AK, which can withstand highmechanical loading, and the inner cable-closure sealing body KDK. Theouter body AK terminates with respect to the laying ground VG below witha standing flange STF and upwardly with a peripheral collar KR. Fittedwithin the collar KR is the outer cover AD, which can be lifted up alonga pivot pin DA and swung out to the side, so that the sealing cover DDof the cable-closure sealing body KDK lying thereunder is thenaccessible. This sealing cover DD seals off the cable-closure sealingbody KDK via a round seal RD and with the aid of a fastener, preferablya bayonet fastener BV. The intermediate space between the outer body AKand the cable-closure sealing body KDK is filled here with a filler, forexample a plastics foam FS. The cable-closure sealing body KDK is holdcentrally in the outer body AK by a spacer AH and the supporting flangeAF for the outer cover. The surface of the laying ground VG,

for example a road surface so, terminates flush with the surface of theouter cover AD, so that a steeples transition is ensured. Shown in theinterior of the cable-closure sealing body KDK is a splice organizer SK,on which the led-in optical waveguides LWL are spliced. After openingthe outer cover and sealing cover, this splice organizer SK isaccessible from above, without the cable closure having to be removed.Because of the excess lengths of optical waveguide, the splice organizerSK can, however, be pulled out for service work. The cables K or elsemicrocables MK are led in through the cable connection units KA1, KA2and KA3 connected downwardly onto the cable closure KMO, these cableconnection units KA1, KA2 and KA3 being angled off, or bent off, at thelaying height of the cables K or MK, so that the leading in can takeplace without buckling. The sealing between the cable K and a cableconnection unit. KA3 may be performed, for example, with the aid of ashrink tube piece SS. The sealing between a microcable MK and unit KA1,which comprises a pipe with introduced optical waveguides, takes place,for example, with the aid of a peripheral crimp connection KV.

In the case of this cable closure according to the invention, however,there may also be provided additional cable connection units from theside in the upper region of the side wall of the cable closure KMO,which units are then usually used for feeding in microcables lying lessdeep, as already described. However, this is not drawn in here. Suchlead-ins may take place radially or tangentially.

Consequently, depending on the type of structural design and layingdepth, cables can be brought together in a cable closure, all the cableends and the associated terminations then being effortlessly accessiblefrom above, without the cable closure itself having to be dug out.

If the static loading, for example in the footpath region, is only low,it is possible to dispense with the outer body. The removable

or pivotable outer cover is then provided directly on the closuresealing body.

What is claimed is:
 1. An optical-fiber transmission system, comprisinga cable closure body and fiber optic cables, said system furthercomprising: (a) cable lead-in spigots, said cable lead-in spigots beingattached to said cable closure body and being in communication with aninterior space of the closure body, said cable lead-in spigots havingrespective outer surfaces; (b) said fiber optic cables comprisingwaveguide-receiving pipes and optical waveguides, saidwaveguide-receiving pipes respectively having outer surfaces and atleast one optical waveguide therein, said waveguide-receiving pipesbeing respectively associated with said lead-in spigots; and (c) saidwaveguide-receiving pipes being connected to said lead-in spigots byrespective sealing connections, said waveguide-receiving pipesterminating at said sealing connection and being disposed exteriorly ofsaid closure body interior space, and respective said waveguides passingsaid sealing connections and entering said closure body interior space,wherein said sealing connections comprise respective sleeves havingrespective interior surfaces, said interior surfaces fittinglycontacting said respective outer surfaces of said lead-in spigots andsaid respective outer surfaces of said waveguide-receiving pipes.
 2. Thesystem of claim 1, said lead-in spigots comprising respective pipes,said waveguide-receiving pipes being respectively in sealing connectionwith the lead-in spigots pipes, said sealing connections thereby formedinhibiting or essentially preventing movement of the cable pipes withrespect to the lead-in spigot pipes.
 3. The system of claim 1, saidlead-in spigots and said waveguide-receiving pipes having respective endsections, said respective end sections being in contact.
 4. The systemof claim 1, said interior space of said closure body comprising a basesection, said base section having a domed shape.
 5. The system of claim1, said interior space being defined by a wall surface of the closurebody, said wall surface comprising at least one ledge for supporting awaveguide tray.
 6. An optical-fiber transmission system, comprising acable closure body and a fiber optic cable, said system furthercomprising: (a) cable lead-in spigots, said cable lead-in spigots beingattached to said cable closure body and being in communication with aninterior space of the closure body, said lead-in spigots having aterminal end section; (b) said fiber optic cables comprisingwaveguide-receiving pipes and optical waveguides, saidwaveguide-receiving pipes respectively having at least one opticalwaveguide therein, said waveguide-receiving pipes being respectivelyassociated with said lead-in spigots, said waveguide-receiving pipeshaving a terminal end section; and (c) said waveguide-receiving pipesbeing connected to said lead-in spigots by respective sealingconnections, said waveguide-receiving pipes terminating at said sealingconnection and being disposed exteriorly of said closure body interiorspace so that respective terminal end sections of the lead-in spigotsand the waveguide-receiving pipes are in contact, and respective saidwaveguides passing said respective sealing connections and entering saidclosure body interior space.
 7. The system of claim 6, said sealingconnection comprising a welded, soldered, crimped, shrink tube, orbonded connection.
 8. The system of claim 6, said interior space of saidclosure body comprising a base section, said base section having a domedshape.
 9. The system of claim 6, said lead-in spigots comprisingrespective pipes, said waveguide-receiving pipes being respectivelysealingly connected to the lead-in spigot pipes, said sealingconnections thereby formed inhibiting movement of the cable pipes withrespect to the lead-in spigots.
 10. The system of claim 6, said interiorspace being defined by a wall surface of the closure body, said wallsurface comprising at least one ledge for supporting a waveguide tray.11. An optical-fiber transmission system, comprising a cable closurebody and fiber optic cables, said system further comprising: (a) aninterior space of said cable closure body, said interior space being atleast partially defined by a wall surface of the closure body, said wallsurface comprising at least one ledge for supporting a waveguide tray;(b) cable lead-in spigots, said cable lead-in spigots being attached tosaid cable closure body and being in communication with said interiorspace of the closure body; (c) said fiber optic cables comprisingwaveguide-receiving pipes and optical waveguides, saidwaveguide-receiving pipes respectively having at least one opticalwaveguide therein, said waveguide-receiving pipes being respectivelyassociated with said lead-in spigots; and (d) said waveguide-receivingpipes being connected to said lead-in spigots by respective sealingconnections, said waveguide-receiving pipes terminating at said sealingconnection and being disposed exteriorly of said closure body interiorspace, and respective said waveguides passing said respective sealingconnections and entering said closure body interior space.
 12. Thesystem or claim 11, said sealing connection comprising a welded,soldered, crimped, shrink tube, or bonded connection.
 13. The system ofclaim 11, said interior space of said closure body comprising a basesection, said base section having a dome shape.
 14. The system of claim11 said lead-in spigots comprising respective pipes, saidwaveguide-receiving pipes being respectively sealingly connected to thelead-in spigot pipes, said sealing connections thereby formed inhibitingmovement of the cable pipes with respect to the lead-in spigots.
 15. Thesystem of claim 11, said lead-in spigots and said waveguide-receivingpipes having respective terminal end sections, said respective endsections being in contact.